In an impact tool which performs a hammering operation or a hammer drill operation by a tool bit on a workpiece such as concrete, dust is generated during operation. Therefore, some conventional impact tools are provided with a dust collecting device for collecting dust generated during operation. For example, Japanese non-examined laid-open Patent Publication No. 2007-303271 discloses a dust collecting device having a cylindrical hood which is arranged to surround a tool bit. In this dust collecting device, dust generated by operation is sucked up through a front end opening of the hood and collected via a pipe and a dust transfer passage formed within the impact tool body.
The above-described known dust collecting device is configured such that the front end of the hood is fixed in position with respect to the tool body. Therefore, for example, when a longer tool bit than usual is used, the distance between the hood front end and a dust generation area is increased, so that the dust collecting efficiency is reduced.